This invention relates generally to a method of tracking material, such as a gravel packing fluid, in a well. In a particular application, the method of the present invention can be used in a simulator for simulating where material will be distributed in a well bore due to a simulated fluid flow through a selected one of several possible flow paths or channels.
While an oil or gas well is being drilled or completed, materials are continually being put into and taken out of the well. For example, drilling mud for lubricating the drill bit and washing cuttings out is circulated into and out of the well as it is being drilled. During stimulation or completion, various treating materials, such as fracturing fluids, acidizing fluids or gravel packing fluids, may be pumped into the well.
It is desirable to keep track of any such materials so that an operator knows what is happening in the unseen downhole environment and whether it is going according to plan. With the increasing use of computers, the ability to track these materials accurately is improving.
Proper control of the drilling or completing of a well is managed not only by tracking actual material movement and disposition in a well, but also by beforehand creating a plan for how and where the material should go and then simulating material movement and disposition to evaluate the plan. Thus, material tracking can and should include both simulated and actual tracking of material in the well under study.
A specific example of where computer-implemented material tracking simulation has been tried is with gravel packing. When sand is produced from a well along with the oil or gas, the sand can cause problems such as equipment damage and reduced production of the oil or gas. One way to inhibit sand production is to pump gravel down into the well so that it packs tightly to minimize the movement of sand grains produced from the formation during the production of oil or gas. The effectiveness of this treatment can be critical to the viability of the well; therefore, properly planning and executing a gravel pack job is important. Tracking material by simulating the pumping in and placement of the gravel pack material is thus desirable for evaluating the likely success of a given plan.
The computer-implemented material tracking simulation methods of which we are aware, specifically those adapted for gravel packing simulations, require large, expensive computers (e.g., a Cray/X-MP computer). These prior proposals must repeatedly calculate and recalculate data during each time at which the material tracking is done. That is, they use iterative problem-solving techniques which require vast computing power to perform the overall method within an acceptable time. The prior methods of which we are aware also typically require significant assumptions which can adversely affect the accuracy of what is simulated compared to what may occur in the actual three dimensional downhole environment. Thus, there is the need for an improved method of tracking material, such as gravel packing fluid or slurry, in a well whereby a smaller, less expensive computer can be used and whereby more accurate three dimensional analysis can be made.